This research is aimed at gaining a better understanding of the genetic control of development and diseases of the central nervous system. Mutant mice are studied by standard light- and electron-microscopic techniques. The main thrust of our research, however, is to study mutant gene expression in experimental chimeric mice. These mice contain mixtures of mutant and genotypically normal cells and allow us to determine in which cell type(s) the mutant genes are acting. Chimeric mice are also being used for studies on cell lineage in the CNS and its role in development and disease.